Copper oxide rectifier



March 14, 1933.

COPPER OXIDE RECTIFIER Filed Sept. 16 1926 Reduqed Co er Lays:

Co er.

Cu rous OX/dc Lq /er.

WITNESSES:

' INVENTOR S Geor e F/v'ar/M. J

G. F. MARTIN, JR 1,901, 3 S

. Z 7 BY I T 'AVT'TO'RNEY' atented Mar. 14, 1933 UNITED s'ra'res EOBGE F. MARTIN, JIL, OF

HOUSE ELECTRIC 8c MANUFACTURING CQMPANY, A

VANIA WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTING- GORPORATION 0F PENNSYL- COPIER OXIDE RECTIFIER Application fi1ed My invention relates to the general class f rectifiers which utilize the asymmetrical urrent-carrying qualities of the junction beween a metal and a compound thereof, such LS an oxide or sulphide.

More particularly, my invention relates to ropper-oxide rectifier-s, which have been found very advantageous in practice, and 1s lirected to methods and means for improvng the neutral or non-rectifying contact be- ;ween the oxide layer and a terminal mem- Jer, the rectifying qualities being developed it the contact between the mother metal and the layer of oxide formed thereon.

My invention will best be understood by reference -to the accompanying drawing, wherein Fig. 1 is a plan view of a metal blank or disc from which my rectifier element is formed;

Fig. 2 is a vertical sectional view therethrough showing, in exaggerated form, the condition of the cuprous and cupric oxide layers after the heating of the blank in air;

Fig. 3 is a similar view showing the con dition of the device after the reduction of the outer or cupric-oxide layer; and

Fig. 4 is a similar view showing a plurality of the discs which have been further treated and assembled to provide a rectifying device, as will A clean copper blank 5, which may be in the form of a circular washer, as shown in Fig. 1, is heated in air, or in an atmosphere containing oxygen, to produce a sufficiently thick oxide coating thereon, the temperature of the heat treatment varying between about 500 C. to the melting point of copper, according to different methods of preparation, although lower temperatures may be utilized within the scope of my invention.

The heat treatment causes the oxidation of the mother metal of the copper blank to produce an inner layer of red oxide of copper, or cuprous oxide, adjacent to the mother metal, and a thin outer layer of black! high-resistance oxide, or cupric oxide, over the outside of the cuprous-oxide layer.

The oxidized copper blank thus prepared is known to have rectifying qualities, trans- As has be subsequently described.

September 16, 1926. Serial No. 135,899.

mitting current much more readily from the cuprous-oxide layer to the mother copper than in the reverse direction. The cupricoxide layer makes a neutral, or non-rectifying, contact with the cuprous-oxide layer, and, as the cupric oxide has a resistance, it is undesirable. Various means and methods have been utilized for remov ing the cupric-oxide layer and for making a neutral, or non-rectifying, contact with the cuprous oxide.

According to my present invention, the cupric-oxide layer is removed, and a good neutral electrical contact is made with the cuprous oxide in a single operation, by the expedient of reducing the cupric-oxide layer to provide a layer of reduced copper in intimate contact with the cuprous-oxide layer. I have found that the contact between the reduced-copper layer and the cuprous-oxide layer is such that-no detectable rectifying qualities can be observed in such contact.

been stated above, however, the contact between the mother metal and the layer of cuprous oxide which is formed thereon is of such nature that current will flow practically only in one direction. According to my invention, therefore, I have provided means for establishing a good, low-resistance electrical contact with the cuprous-oxide layer, without destroying the rectifying qualities of the device.

I have found that the most desirable method of providing the reduced-metal layer just described is to quench the heated oxidized plate in a mineral oil and I have found it desirable to use oil which has been aged by long heating at a low temperature before quenching the plate therein. While I now prefer mineral oils, it is entirely possibleto utilize vegetable oils or mixtures of oils, or other organic or inorganic compounds, either liquid or gaseous, which are decomposable to produce a reducin agent upon contact with the hot oxidized plate. I have used gasoline, alcohol and even natural gas, but I am obviously not limited to the materials specifically mentioned. When oil is utilized, it is believed that local cracking results from the contact with the relatively high hot plate and the decomposition products reduces a portion of theoxide coating to produce a thin layer of reduced copper. The metallic copper so formed comprises a firmly adherent film which makes an excellent contact with the cuprous-oxide layer of the rectifier.

After the preparation of the discs, as hereinabove described, they are treated, by any suitable means, such as sand blasting, to remove the layers of oxide and reduced copper from one side of the blank and, preferably, also from the side edges thereof. A plurality of the discs thus treated may be superposed to provide a rectifier which is.

able to withstand any desired counter-electromotive force, and the whole assembly may be clamped, by means of an insulated bolt 11, between two end plates 12 and 13, to which terminal conductors are attached, as indicated at 14 and 15, the direction of current flow being indicated by the arrows.

As a concrete example of the precise process which I now prefer, I heat the copper plates in a furnace to a temperature of 925 C., or, in general, to a temperature between 900 C. and 1000 C. or temperatures of that order, for from one-half hour to one hour. I then cool the furnace rapidly to 700 C., and then take the plates out and immediately quench them in oil at room temperature, the oil, in this case, being a mineral oil having a parafline base. There is an apparently critical temperature, which is, in general, different for each oil, or rather for each reducing or quenching agent, at which the oxidized plate must be, when it is quenched. It is necessary, for each quenching fluid, to make a few tests, with oxidized plates at different initial temperatures, and to test each plate for its rectifying property, or ratio of the current in one direction to the current in the other, in order to determine the most desirable temperature, as vastly superior results will be obtained by observing the critical temperature conditions for quenching.

While I have described my invention as a contact rectifier or asymmetrical currentconductor, it is to be understood that two contact rectifiers may be connected in opposition to provide a condenser for alternating-current circuits, and I intend that the expression contactrectifier in the appended claims shall embrace the use of the device in a condenser or any other uses to which it may be put.

In the foregoing description, I have referred to the inner layer of red oxide as cuprous oxide, and the outer layer of black oxide as cupric oxide. While I have employed the terms cuprous and cupric", in the specification and claims, to refer to these oxide layers, I do not mean to specify that either layer is a pure, homogeneous compound, or that cupric oxide or eve normally unstable oxides may not be at mixed in the layer which I designate a cuprous oxide.

Although I have shown and described m; process and apparatus in a preferred em bodiment thereof, it is to be understood tha it is not limited thereto, as many change and modifications will readily suggest them selves to the skilled Workers of the art. I desire, therefore, that the appended claim: shall be accorded the broadest interpretation consistent With their wording and tln state of the art.

I claim as my invention:

1. The step in the method of preparing a unidirectional current-carrying device which comprises quenching a hot oxidized metal electrode in oil.

2. The step in the method of preparing a unidirectional current carrying device which comprises quenching a hot oxidized copper electrode in oil.

3. The step in the method of preparing a unidirectional current-carrying device which comprises treating a hot xidized copper electrode at the critical temperature in an agent which is decomposable at the temperature of said heated electrode to provide a reducing agent capable of forming a layer of reduced metal on the oxide layer.

4. The method of preparing a unidirectional current-carrying device which comprises heating a copper plate in an atmosphere containing oxygen to produce an oxide layer on the mother copper of the plate, 7

quenching the heated oxidized plate in an agent which is decomposable at the temperature of said heated plate to provide a reducing agent capable of forming a layer of 1 reduced copper on the oxide layer, and making terminal contacts with the mother copper and the reduced copper, respectively.

5. The method of preparing a unidirectional current-carrying device which comprises forming a layer of oxidized metal on the mother metal of. a metallic electrode, heating the oxidized electrode, quenching the heated electrode in an agent which is decomposable at the temperature of said'heated electrode to provide a reducing agent capable of forming a layer of reduced metal on the oxide layer, and making terminal contacts with the mother metal and the reduced metal, respectively.

6. The method of preparing a unidirectional current-carrying device which comprises treating'a copper electrode to produce an oxide layer on the mother copper of the electrode, quenching the heated electrode in a mineral oil to produce a layer of reduced copper on the oxide layer, and making terminal contacts with the mother copper and the reduced copper, respectively.

heating the oxidized electrode, 134

7. The method of repa g a unidirec tional current conductlng device which comprises heating a copper blank to form an outer layer of cupric oxide and an inner layer of cuprous oxide on the mother metal of the blank, reducing the cupric-oxide layer .0 produce a layer of reduced copper on a cuprous-oxide layer which is in turn in contact with the mother copper on which it was formed, and making terminalcontacts with the mother copper and the reduced copper, respectively.

8. The method of preparing a metal for utilizing the rectifyin qualities between a metal andits oxide, W ich comprises forming a layer of oxide on the metal and relucing a portion of the oxide layer to provide a layer of the reduced metal thereon.

9. The method of preparing metal for utilizing the rectifying qualities between a metal and a chemical compound thereof, which comprises forming a layer of the compound on the metal and reducing a portion of the layer of the compound to provide a layer of the reduced metal thereon.

10. The method of making contact with a metal com ound in a contact rectifier, comprising pro ucing a layer of reduced metal on the compound by reducing a portion of said metal compound.

11. The method of making a substantially non-rectifying contact with an oxide of a metal constituting an element of a contact rectifier, comprlsing producing a layer of "educed metal on the oxide by reducing a portion of said metal compound.

12. The method of making a substantially non-rectifying contact with an oxide of copper constituting an element of a contact rectifier, comprising1 producing a layer of reduced metal on t e oxide by reducing a portion of said metal compound.

13. A unidirectional current-carrying device comprising a metal member, an oxide layer'consisting of an oxidized portion, of said metal member in contact therewith, a reduced-metal layer consisting of a deoxidized portion of said oxide layer,-and means for carrying current to or from said 'educed-metal layer and said metal member, respectively. 7

14. A unidirectional current-carrying device comprising a copper member, an oxide layer consisting of an oxidized portion of said copper member in contact therewith, a reduced'copper layer consisting of oxidized portion of saidoxide layer, and means for carrying current to and from said reduced-copper layer and said copper member, respectively. I

15. A unidirectional current-carrying device comprising ametal member, a layer of a chemical compound of said metal consisting of a treated portion 'of said metal member in contact therewith, a reduced-metal 'oxide of a metal,

rents, a layer of copper,

a de-.

treated portion of said layer consisting of a and means for carrylayer of compound, ing current to or from said reduced-metal layer and said metal member, respectively.

16. A contact rectifier comprising a metal compound and a layer of reduced metal from the metal compound on the compound. k 17. The combination with a contact recti fier comprising, as one element thereof, an

of means for making a contact with said oxide, a layer of reduced metal oxide on the oxide.

18. The combination with a contact rectifier comprising, as one element thereof, an oxide of copper, of means for making a substantially non-rectifying contact with said oxide, said means'com'prising a layer of reduced metalfromthe oxide on the oxide.

19. The step in the method of preparing a unidirectional current-carryin device comprising copper having an oxi ized surfrom the metal said means comprising face which consists in subjecting said oxient.

20. The method of preparing a device, possessing a unilateral electrical conductivity which comprises heating a copper blank to approximately 1000 (3., subjecting it while so heated to the action of an oxidizing agent and subsequently subjecti'n the surface thereof to the action of a re ucing agent.-

21. A rectifying element for alternating electric current comprising a metallic mass having an oxidized surface which latter has been reduced to a metallic form on its exosed surface.

22. The process of forming .a valve for electrical currents which comprises oxidizing the surface of a copper element at an elevated temperature, and subsequently sub- 'ecting the element to the quenching action of a reducing liquid reagent to form a copper layer. on the outside of the oxidized copper.

23. An electrical rectifying unit, comprising a layer of red copper oxide disposed between layers of elemental copper forming an integral unit.

24. In a valve for alternating electric cura layer of copper oxide formed thereon by oxidation of the copper. and a layer of copper formed on the copper oxide layer by reduction of the coper oxide.

- 25. The process of forming a valve for alternating electric currents which comprises oxidizing the surface of a copper element, and subsequently subjecting the oxide to the action of a reducing reagent to form a copper layer on the outside of the. copper oxide.

26. The process of forming a valve for alternating electric currelrts, which comprises forming on the surface of a metal element a layer of oxide of the metal, and reducing a portion of the oxide la er to provide a layer of the reduced metal t ereon;

he process of forming a valve for alternating electric currents w ich comprises 5 forming on the surface of a metal element a layer of a chemical compound of the metal and reducing a portion of the layer of the v compound to provid'ea layer of the reduced metal thereon. v 1 28.'The process of forming a valve forv alternatin electric currents which c'omprises oxi izing the surface of a copper element by exposure to heat and oxygen and cooling in two stages, first'without reduc- L15 tion and then in contact with a quenching reducin reagent.

29. The process of formin a valve for alternating electric currents w 'ch comprises oxidizing the surface of a copper element .20 by heating to a temperature as high as bright red heat and cooling to a temperature ma terially lower but sulficiently high to cause a layer of reduced copper to be formed on the outer surface of the oxide layer upon 25 quenching with a reducing reagent, and

thereupon so quenching the element.

In testimony whereof, I have hereunto subscribed my name this 11th day of September 1926.

30 GEORGE F. MARTIN, JR. 

